Java Referring to any object

Question

I would like to find an object. There is only one object with the variable x=10. Is it possible? I hope you get what I try to explain... :)

if (any object of the class X .getValue() == 10)
...

Class X

 public int getValue(){
    return x;
    }

You want to find it from where? a list, database, etc? please post some more of your code for clarity. — Avinash Anand, Apr 14 '18 at 19:30
In your program you need to somehow store instances of Class X. In order to answer your question you need to tell us what data structure you are using to hold those instances of X — luksch, Apr 14 '18 at 19:32
[Getting all instances of a class](//stackoverflow.com/q/10071065) maybe? Or do you want `static`? — 001, Apr 14 '18 at 19:38

Rakesh Narang · Answer 1 · 2018-04-14T19:41:55.953

0

List<X> xList = new ArrayList<>();

public static X findXWithValue(List<X> xList, int value) {
 X xWithValue = null;
 for(int i = 0 ; i < xList.size()-1 ; i++) {
  if (value == xList[i].getValue()) {
   xWithValue = xList[i];
   break;
  }
 }
 return xWithValue;
}

Br,

Rakesh

edited Apr 14 '18 at 19:41

answered Apr 14 '18 at 19:35

Rakesh Narang

79
1
8

`List xList = new ArrayList<>();` - [Don't use raw types.](https://stackoverflow.com/questions/2770321/what-is-a-raw-type-and-why-shouldnt-we-use-it) – Turing85 Apr 14 '18 at 19:39
Actually the code was not formatted, because of which the was hidden. – Rakesh Narang Apr 14 '18 at 19:42

score 0 · Answer 2 · answered Apr 14 '18 at 20:03

Something like:

public class ObjectFinder {

public static boolean checkObject(Object o, String methodName, int value) {
    return Stream.of(o.getClass().getDeclaredMethods())
            .filter(method -> method.getName().equals(methodName))
            .filter(m -> checkType(m, int.class))
            .map(m -> {
                try {
                    return (int) m.invoke(o);
                } catch (IllegalAccessException | InvocationTargetException e) {
                    e.printStackTrace();
                    return 0;
                }
            }).anyMatch(v -> value == v);
}

private static boolean checkType(Method method, Class type) {
    return method.getReturnType() == type;
}

}

and you can test it in:

public static void main(String[] args) {
        System.out.println(checkObject(new X(), "valueOf", 2));
    }

Java Referring to any object

2 Answers2